Two-wheeled, push-drive, ride-on locomotion units for manually steerable utility vehicles are known in the art as represented by U.S. Pat. No. 4,771,840 issued to R. A. Keller on Sep. 20, 1988. This power drive unit is articulated at a ball joint to a manually steerable shopping cart, and comprises a variable speed electric motor. A riding seat is located forwardly of the motor to put a downward load on the coupling shaft, which varies with the weight of a rider, and loads down the rear wheels of the four wheeled shopping cart. An axle to which the two drive wheels are affixed is driven by the motor through an intermediate conventional differential.
This type of push-drive locomotion presents many heretofore unsolved problems in the art. For example, it is a deficiency that the tractor unit disturbs the loading of the driven utility vehicle. Also, when the rider must be extremely alert in any attempt to drive the utility vehicle in a straight line, that is a significant disadvantage. Furthermore these push-drive units make steering difficult in that wheels affixed to an axle for driving without independent rotation of the separate wheels introduces tracking problems and thus erratic steering may result that must be corrected by the driver by appropriate compensatory manipulation of the driven utility vehicle. Nor is there in this exemplary prior art provision for bi-directional drive or reverse movement.
Accordingly, this invention has the objective of providing improved push-drive locomotion units.